Chamber aligning device for splitchamber automatic shotguns



E. P. SIMMONS 2,920,537

2 Sheets-Sheet 1 CHAMBER ALIGNING DEVICE FOR SPLIT-CHAMBER AUTOMATIC SHOTGUNS Jan, '12, 1960 Filed May 12, 1958 INVENTOR 5mm Prim/1100.;

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Jan, 12, 1960 SIMMONS 2,920,537

CHAMBER ALIGNING DEVICE FOR SPLIT-CHAMBER AUTOMATIC SHOTGUNS Filed May 12, 1958 2 Sheets-Sheet 2 INVENTOR [rweuf flJim/no/w A fro/we y.

CHAMBER ALIGNING DEVICE FOR SPLIT- CHAMBER AUTOMATIC SHOTGUNS Ernest P. Simmons, Kansas City, Kans.

Application May 12, 1958, Serial No. 734,588

3 Claims. (Cl. 89--156) This invention relates to new and useful improvements in shotguns, and has particular reference to automatic shotguns of the split chamber type.

In guns of this type the barrel does not recoil relative to the receiver. Instead, the chamber is separate from the barrel, being slidably mounted in the rearward portion of said barrel for limited rearward movement, and the bolt is carried and locked in a rearward extension of the chamber which projects into the receiver. When the gun is fired, the chamber, chamber extension and bolt recoil rearwardly as a unit for a short distance. The impetus given to the bolt by this short travel actuates mechanism which unlocks the bolt from the chamber extension, and whereby the 'bolt is carried on rearwardly in the chamber extension. This extended travel of the bolt is of course necessary in order that the process of extracting and ejecting the expended shell case may be performed thereby. However, difiiculties have arisen in the performance of this gun in that both the chamber and its extension are essentially cylindrical, and are therefore rotatable respectively in the barrel and the receiver. Ordinarily, they are prevented from tuming to any great degree out of angular alignment by the presence of the bolt in the extension, since said bolt is disposed within the inverted U-shape of the chamber extension, and since said bolt is separately guided in the receiver. However, the bolt must fit very loosely in the chamber extension in order that it may move freely, and it therefore sometimes occurs that while the bolt is in a rearward position, the chamber member may turn slightly about its axis so that portions thereof, particularly the lower ends of its inverted U-shape configuration, may extend into the path of the bolt, or parts associated with and movable with the bolt, so as to block and prevent forward movement of the bolt. locked out of battery and cannot be fired again until the chamber has been manually turned to allow forward movement of the bolt.

The primary object of the present invention is therefore the provision, in a gun of the character described, of novel means operable to index the chamber and its extension accurately with relation to its angular disposition about its axis, and to prevent turning of said chamber about its axis during any portion of the operating cycle of the gun.

Other objects are simplicity and economy of construction, efliciency and dependability of operation, and adaptability for application to pre-existing guns with a minimum of alterations.

With these objects in view, as well as other objects which will appear in, the course of the specification, reference will be had to the drawing, wherein:

Fig. 1 is a longitudinal vertical sectional view of a split-chamber automatic shotgun embodying the present invention, with portions left in elevation and portions broken away showing all parts thereof in readiness for firing, I I

Fig; "2' is 'a view similar to Fig. 1, but showing the The gun is therefore parts thereof during the firing cycle with the bolt at its rearwardmost point of travel,

Fig. 3 is a slightly irregular fragmentary sectional view taken on line III-III of Fig. 2,

Fig. 4 is a fragmentary sectional view taken on line IV-IV of Fig. 1,

Fig. 5 is a fragmentary sectional view taken on line VV of Fig. 2,

Fig. 6 is a fragmentary sectional view taken on line VI-VI of Fig. 1, and

Fig. 7 is a view similar to Fig. 6, and showing a slightly is closed by a trigger frame 10 secured in the receiv'erby, an assembly pin 12, and the forward portion of said bottom opening is occupied by a trough-like shell carrier 14 which is pivoted at 16 to frame 10 on a horizontal axis transverse to the gun, and the general operation of which will be set forth below.

The gun barrel 18 is threaded into the forward end of the receiver, and communicates therewith. A magazine tube 20 is disposed beneath and parallel to the barrel, and is also threaded into the receiver. A magazine spring 22 disposed inside said tube urges a follower cup 24 slidably rearwardly, whereby a shell or shells 26 in said magazine are urged rearwardly'into receiver 2 over carrier 14, as will be described.

A cylindrical chamber 28 is disposed rotatably and slidably in the rearward portion of barrel 18, and adapted to receive a shell 26 therein, said chamber being provided with an internal shoulder 30 against which the rim 32 of the shell seats, and an external shoulder 34 which abuts the rearward end'of the barrel to limit forward movement of the chamber. Said chamber is provided with an integral rearward extension designated generally at 36 and being of generally inverted U-shape as best shown in Fig. 5, having a top wall 38 and depending right and left side walls 40 and 42. Externally, said chamber extension is cylindrically curved coaxially with. the barrel and chamber, and is normally rotatable about its axis in the receiver. The rearward end of the ex tension is normally disposed in forwardly spaced re-v lation from a forwardly facing internal shoulder 44. A pin 46 parallel to the axis of the extension is disposed slidably in a bore 48 formed in the rearward end of left side wall 42 of the extension, as best shown in Figs. 1 and 6. A spring 50 in the base of said bore urges said pin rearwardly against shoulder 44, whereby the chamber is urged forwardly.

The bolt 52 is normally disposed within chamber extension 36, the forward end of said bolt resting against the base of the shell 26 within the chamber. Said bolt is also provided on its upper side with a lug 54 which projects into a slot 56 in top wall 38 of the extension, whereby to lock the bolt against rearward movement. The bolt has right and left depending side walls 58 and 60 each having a slot 62 formed therein, the forward portion of said slot being horizontal, and the rearward being disposed for forward and rearward sliding movement in grooves 70 and 72 formed respectively in the inner surfaces of receiver side walls 4 and 6. A connecting link 74 is pivoted on pin 64 between the side walls of the] Patented Jan. 12, 1960 of the gun. A return'spring; not-"shown, is also carried in the gunstock and urges rod 7'8 forwardl y'at all times.

The-structure-thus far described is well known.- Although many specific features thereof" are not essential tot-the present invention,- a cycle of operation thereof will be sketched inorder to facilitate a readyunderstanding ofthe invention; With the parts positioned for firing as shown in Fig. 1, it will be seen that the rearmost shell 26 111 magazine 20 isprevented frombeing moved rearwardly onto carrier 14 by a tang 84 depending'from'jthe forward end'of the-bolt. When the trigger '86 is pulled, it actuates an ordinary sear, not shown, carried in frame I0-, whichf-releases -ahammer 88 also pivoted in said frame: Said lhammer pivots upwardly and forwardly, and strikes therearward-end' of a firing pin; 90 extending longitudinally through the bolt. The firing, pin is thereby projected through the forward end of the bolt and detonates the shell 26 inchamber 28.

Since the-bolt is locked inthe chamber extension by lug 54,;the force of recoil is transmitted to said extension, andthe extension and chamber recoil also, against the pressure of spring 50', until said extension strikes shoulder 44, whereby its movement is arrested and whereupon it is immediately returned forward by spring 50. During the short chamber movement, bolt 52 is in engagement with pin 64, and delivers a'rearward impulse through said' pin-and link 74 to inertia rod 78. When the chamber is stopped, rod- 78 continues rearwardly by inertia. When'ipin 64-has traversed the forward horizontal portions of slots 62 and entered the rearward inclined portions' ofthe slots, it acts on the slot walls to cam the rearward end of the bolt downwardly to disengage lug 54 from slot 56 of the chamber extension, Continued-rear ward movement of inertia rod 78 carries the bolt rearwardl'y" to the position shown in Fig. 2. During this boltmovement, an extractor'92 carried by the bolt removes the expended shell case from the chamben an d an ejector, not shown, flips said shell case transversely through an opening 94 formed in right side wall 40 of the chamber extension (see Figs. 2 and 4), and through a-matching opening 96 formed in right side wall 4 of the receiver. Also during the rearward bolt movement, the bolt tang 84 is moved out of the path of the'rearmost shell 26 in magazine 20, and said shell is moved rearwardly onto carrier 14 by magazine spring 22. The rearward'movement of the bolt also re-cocks hammer 88.

When the bolt is again moved forwardly by the return spring in the gunstock, it engages a dog 98 pivoted to the rearward end of carrier 14, so that carrier 14 is elevated to raise the shell carried thereby into the path of the bolt, so that as the forward movement of the bolt continues, it'pushes said shell into the chamber, and pin 64-acting in cam slots 62 raises locking lug 54 into extension slot 56 to lock the gun in battery, and the gun is again ready for firing.

' The foregoing description of the gun operation is somewhat sketchy, but is'believed adequate for an understanding of the present invention. It will be seen that the only thing which prevents turning of the chamber and its extension about its axis: is that the bolt, and right slide 66;are disposed between the'side walls 40 and 42 of the chamber extension, 'as best shown'in Figs. 4 and 5. However, when the bolt is fully retracted as shown in Fig. 2, the slides are disposed 'rearwardly from the chamber ex tension, and the bolt fits loosely in the extension. Hencethe chamber extension is free at this time to turn slightly about"its"axis,' and often does so under the shaking and vibration caused "by the gun operation. As a consequence, the lower rear corners of side walls 40 and 42 of the chamber extensionmay move into the path of the slides, so-as totblockv forward movement of said slides,

thereby jamming the action by preventing the bolt from moving forwardly into battery position. The commonest point of interference has been that the lower rear corner 100 of side wall 40 (see Figs. 2, 3, 4 and 5) moves into the path of the upper forward corner 102 of right slide 66, or that the lower rear corner 104 moves into the path of the upper forward corner106 of left slide 68.

The present invention absolutely prevents these occurrencesby preventing the turning of the chamber and extension about their axis at all times. In the species of my invention shown in Figs. ,1 to 6, I have atfixed a rearwardly extending finger 10 8 rigidly to the rearward edge of the top wall 38'of the chamber extension, and formed a notch 110* in the top wall 8 of the receiver. Said notch opens through the shoulder 44 of the recevier, and finger 168 is engaged snugly but, slidably therein. Thus it will be seen that While said finger in'no way inhibits the motion of the chamber extension as previously described, or with the normal operation of any other'part, it does positively restrain theextensi'on against turning, about its axis, and thereby-prevents the malfunction above discussed;

The problem is not; as simple as it would at first appear. For'reasons ofmanufacturing requirements, it is' not practical to make the chamber andextension in any shape other than cylindrical. Moreover the walls o-f-the-chamber, chamber extension and adjacent portions of the barrel and receiver, are so thin that to use tongue and groove or key-type rotation locks would objectionably weaken these walls and reduce their ability to withstand the tion is simple, completely effective, "economical, and

avoids dangerous weakeningof any part subject to heavy stress. Moreover, it is applicable to virtually any preexisting gun of this type, with a minimum" amount of alteration and expense.

Inthe species of the invention shown in Fig. 7, the chamber return pin is utilized as the rotation lock. This pin, designated at 112, is somewhat longer than the cor responding pin 46 in the standard gun, and the receiver shoulder 44 has a socket 114 bored thereinparallel to the gun axis for receiving the rearward end portionof said pm; tion of returning the chamber forwardly after each recoil, but also positively. prevents the chamber and extension from turning about their axis.

While I have shown and described a specific embodi ment of my invention, it will be-re'adily' apparent'that numerous'minor changes-of structure and operation could be made Without departing from the spirit of the inven{ tion as defined by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent is:

1. A chamber aligning device for use "in connection with an automatic shotgun having a hollow receiver, a

barrel fixed in said receiver, a cylindrical chamber morn ber disposed coaxially in said barrel for limited axial sliding movement therein and normally being free to turn to some degree about its axis and a chamber extension fixed to said chamber member and projecting into said receiver, efficient operation requiring that said'chamber and extension be restrained against turning' about the ber member and its extension about the axis of saidchamber member.

2. A device as recited in claim 1 wherein rearward Thus the pin 112 serves not onlythe usual func axial movement of said chamber extension is limited by a forwardly facing shoulder formed in said receiver, and wherein said socket is formed in said shoulder and said finger is attached to the edge of said chamber extension operable to abut said shoulder.

3. A device as recited in claim 2 wherein said finger is disposed for axial sliding movement in a bore formed in said chamber extension parallel to the axis of said chamber, and with the addition of a spring urging said finger resiliently toward said shoulder, said finger being urged at all times into said socket by said spring.

References Cited in the file of this patent UNITED STATES PATENTS Febiger Aug. 15, 1905 Mason May 21, 1907 Williams Aug. 19, 1958 

